Continuum robots are widely applied in minimally invasive interventions through natural orifices of the human body. The challenge of poor distal positioning accuracy in flexible continuum robots, along with a lack of precise navigation methods, is recognized. In response, a multi-segment continuum robot shape reconstruction method based on electromagnetic positioning information is proposed, aimed at achieving accurate end navigation and positioning. An efficient shape reconstruction method for a two-segment active structure, based on third-order Bézier curves, was introduced. The solution of Bézier curves was optimized as a nonlinear least squares problem and was quickly and accurately solved by a particle swarm algorithm with linearly decreasing weight. The method proposed allows for the accurate fitting of the shape of dual-segment continua. And has good real-time performance. The results show that within the bending angle process, the average root-mean-square error of shape reconstruction is 0.48 mm, which is 0.8% of the length of the continuum bending segment. The accuracy and reliability of the proposed shape reconstruction method for intracavitary interventions using micro-continuum robots are demonstrated through detailed modeling and validation results.